Oral Supplementation of Collagen Peptides Improves Skin Hydration by Increasing the Natural Moisturizing Factor Content in the Stratum Corneum: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial.

INTRODUCTION: We aimed to investigate the effect of orally ingested collagen peptides (CPs) on skin condition and elucidate their mechanism of action. METHODS: A randomized, placebo-controlled, double-blind trial was conducted in 99 healthy Japanese women, aged 35-50 years. The subjects were randomized into 3 groups (33 subjects/group) to receive 1 or 5 g of CP or placebo once daily for 12 weeks. Skin water content, transepidermal water loss (TEWL), skin elasticity, and skin thickness were evaluated before treatment and after 4, 8, and 12 weeks of treatment. The level of natural moisturizing factor (NMF) constituents in the stratum corneum (SC) was quantified before treatment and after 12 weeks of treatment. RESULTS: Oral ingestion of CP increased the water content in the SC and epidermis and decreased TEWL. Furthermore, the NMF level in the SC was increased. However, skin elasticity and skin thickness remained unchanged. CONCLUSIONS: The improvement in skin water content following the oral ingestion of CP can be attributed to an increase in the level of NMF in the SC. TRIAL REGISTRATION: UMIN000030375 (retrospectively registered).

The corrected structure of depressoside, an antioxidative iridoid glucoside extracted from the flowers of Gentiana urnula Harry Sm.

Three known iridoid glucosides (gentiournoside A, gentiournoside E and depressoside) were isolated from the flowers of Gentiana urnula Harry Sm. through activity-guided fractionations with a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. All three compounds exhibited excellent DPPH radical scavenging activities (IC50: 10-20 µmol L(-1)) comparable to that of ascorbic acid and Trolox. However, examination of the NMR data revealed that the reported chemical structure of depressoside, previously isolated from the leaves of G. depressa, needed correcting due to incorrect elucidation around C-7 of the iridane skeleton, and was corrected to 6-ß-(2,3-dihydroxyphenyl)-D-glucosyl 7-O-(2,3-dihydroxybenzoyl)-loganate. Depressoside exhibited a much higher scavenging activity against superoxide radicals (IC50: 45.5 µmol L(-1)) than the other two extracted compounds (IC50: more than 900 µmol L(-1)) due to the crucial presence of a pyrogallyl unit.